This invention relates generally to multiple component polymeric compositions and, more particularly, to multi-component networks or membranes containing hydrophilic, lipophilic and oxyphilic segments or domains, wherein at least one of the segments include poly(ethylene glycol).
Many medical deficiencies and diseases result from the inability of an individual""s cells to produce normal biologically active moieties. Many of these deficiencies can be remedied by providing an exogenous source of needed biologically active moieties or pharmacological agents to the individual having the deficiency. A well known example of a disease that can be remedied by providing an exogenous source of a biological material or pharmacological agent is Type I diabetes mellitus, wherein the production of insulin by pancreatic Langerhans islets is substantially deficient, impaired or completely lost.
Advances in cell and tissue engineering has also led to the development of bioartificial organs as potential approaches for ameliorating a variety of these medical deficiencies. Progress made in biomaterial research over the past several years has indicated that synthetic organic polymers may be the future of artificial organ research. For instance, using the Type I diabetes example above, encapsulation of human islet cells or tissues within a biologically compatible (biocompatible) device, such as a reservoir or physical barrier, followed by implantation of the device within an individual has been proposed to deliver biological material to an individual to treat Type I diabetes and other disease states.
While hundreds of different polymer structures exist, only a few are the focus of biomaterials research. This is because, while many polymers may approximate some of the properties required for use as artificial organs, most are not ideal in that they lack the combination of properties needed. For example, silicone rubber is a well known material used in medicine because of its inert behavior, transparency and flexibility. But for certain applications, e.g., for use as a tracheal prostheses, a hydrophilic surface is required, and silicone rubber is not hydrophilic. Similarly, in the Type I diabetes example, the immune response of the host and, consequently, the graft rejection of biological materials such as cells, tissues and organs, has severely limited the use of implantation of many materials into individuals. The biomaterials employed to contain the foreign cells must be at least amphiphilic, in other words permeable to water and to hydrocarbons, but must not let the immune response of the host destroy the cells or tissues therein.
Heretofore, amphiphilic polymer networks have been targeted as potential materials that may be useful for implantation of biologically active moieties. Such amphiphilic polymer networks are random, co-continuous assemblages of hydrophilic and hydrophobic polymer chains that are able to swell in both hydrophilic solvents (e.g., water) and hydrophobic solvents (e.g., a liquid hydrocarbon). Because these materials swell in water, they generally fall into a class of compounds known as xe2x80x9chydrogelsxe2x80x9d.
The first amphiphilic membranes for biomaterials were developed over a decade ago with the advent of living carbocationic polymerzation. The syntheses of these polyisobutylene-based amphiphilic networks were accomplished by the free radical copolymerization of a variety of inexpensive, commercially available monomers (e.g., N-dimethylaminoethyl methacrylate, dimethyl acrylamide) that gave hydrophilic polymers with the hydrophobic crosslinking agent, di-methacryl-telechelic polyisobutylene (MA-PIB-MA). A more detailed discussion on amphiphilic networks may be found in Keszler and Kennedy, Journal of Macromolecular Science, Chemistry Edition, Vol. A21, No. 3, pages 319-334 (1984), the disclosure of which is incorporated herein by reference.
Continued research in the area led to the development of other PIB-based amphiphilic networks, many of which are implantable and quite similar in use to controlled drug-release devices. They both must be bioinvisible, must have controlled pore sizes, must allow the diffusion of desirable well-defined molecules, must be sterilizable, and must have robust mechanical properties for implantation, use and retrieval.
For example, Kennedy, U.S. Pat. No. 4,486,572 discloses the synthesis of styryl-telechelic polyisobutylene and amphiphilic networks comprising the copolymerization product of the styryl-telechelic polyisobutylene with vinyl acetate or N-vinyl-2-pyrollidone. Kennedy, U.S. Pat. No 4,942,204 discloses an amphiphilic copolymer network swellable in both water and n-heptane but insoluble in either, comprising the reaction product of an acrylate or methacrylate of a dialkylaminoalkyl with a hydrophobic bifunctional acryloyl or methacryloyl capped polyolefin. The preferred embodiment disclosed is an amphiphilic network having been synthesized by the free-radical copolymerization of a linear hydrophobic acrylate (A-PIB-A) or methacrylate capped polyisobutylene (MA-PIB-MA) with 2-(dimethylamino)ethyl methacrylate (DMAEMA). In a continuation-in-part to U.S. Pat. No. 4,942,204, Ivan et al. U.S. Pat. No. 5,073,381 discloses various amphiphilic copolymer networks that are swellable in water and n-heptane that comprise the reaction product of a hydrophobic linear acryloyl- or methacryloyl- capped polyolefin and a hydrophilic polyacrylate or polymethacrylate, such as N,N-dimethylacrylamide (DMAAm) and 2-hydroxyethylmethyl methacrylate (HEMA).
In addition, Hirt, U.S. Pat. No. 5,807,944 discloses an amphiphilic segmented copolymer of controlled morphology comprising at least one oxygen permeable polymer segment and at least one ion permeable polymer segment, wherein the oxygen permeable segments and the ion permeable segments are linked together through a non-hydrolyzable bond. The oxygen-permeable polymer segments are selected from polysiloxanes, perfluoroalkyl ethers, polysulfones, and other unsaturated polymers. The ion permeable polymers are selected from cyclic imino ethers, vinyl ethers, cyclic ethers, including epoxides, cyclic unsaturated ethers, N-substituted aziridines, xcex2-lactones, xcex2-lactanes, ketene acetates, vinyl acetates and phosphoranes.
More recently, U.S. application Ser. No. 09/433,660, owned by the assignee of record, has disclosed an amphiphilic network comprising the reaction product of hydrophobic crosslinking agents and hydrophilic monomers wherein the hydrophobic crosslinking agents are telechelic three-arm polyisobutylenes having acrylate or methacrylate end caps and wherein the hydrophilic monomers are acrylate or methacrylate derivatives.
However, while amphiphilic networks provide the necessary hydrophilic and hydrophobic components necessary to conceive suitable biomaterials and devices, there are other areas where the biomaterials or membranes produced from the amphiphilic networks were not suitable. For instance, while the amphiphilic networks of the prior art are, in most instances, permeable to water and hydrocarbons, they are not highly permeable to oxygen.
It is, therefore, believed desirable in the art to develop networks and/or implantable biological devices that have superior immunoisolatory properties, superior mechanical properties, and are biocompatible, hemocompatible, and exhibit excellent biostability when placed into a host for extended periods of time, and which are hydrophilic, lipophilic and oxyphilic (hereinafter xe2x80x9ctriphilicxe2x80x9d).
The multiple component networks (MCNs) of the present invention should be distinguished from more traditional interpenetrating polymer networks (IPNs). An MCN is defined as a single elastomeric network comprising at least two chemically different covalently-bonded sequences; whereas, an IPN consists of two or more unlinked, independent networks. The distinction is significant because the polymers in the IPNs are not linked chemically; instead, they are two separate networks tangled within one another. The distinction between MCNs and IPNs is more particularly set forth schematically hereinbelow, wherein the networks are bicomponent networks. 
Traditionally, MCNs require that the two or more crosslinked components contribute to the physical and chemical characteristics of the polymeric networks. To that end, it will be appreciated that bicomponent networks have chains consisting of two chemically different moieties, while tricomponent networks have chains consisting of three chemically different moieties. The properties of the multicomponent networks will reflect those of its individual components.
Bicomponent networks are known in the art. Earlier inventions showed that polyisobutylene (PIB) in combination with various other segments, including polydimethyl siloxane (PDMS), methacrylate and siloxane, and hydrophilic acrylates, leads to biocompatible materials and even amphiphilic networks. Others have synthesized PIB-PEG networks via isocynate chemistry. However, almost all of the development relating to bicomponent networks has been based upon the carbocationic polymerization of polyisobutylene. Moreover, while bicomponent networks are known, there is little, if any, information relating to tricomponent/tricontinuous networks in the literature.
Thus, it is also believed desirable to synthesize semipermeable, biocompatible and immunisolatory membranes which are not limited to polyisobutylene-based chemistry, but yet retain the triphilic characteristics and mechanical properties desired of such membranes.
At present, there are many compounds that could be useful as biocompatible segments in multicomponent networks. For example, poly(ethylene glycol) (PEG) is a water soluble polymer showing excellent biocompatibility and has been frequently used in biomedical applications. Similarly, polysiloxanes are widely used in the biomedical field and have been the subject of intense study both in the academic field as well as in industry.
Heretofore, however, there has been little, if any, study of these or other compounds for use in amphiphilic networks or other multicomponent networks without PIB.
It is, therefore, an aspect of the present invention to provide a multicomponent network of at least two chemically different components or segments covalently bonded together.
It is another aspect of the present invention to provide a multicomponent network, as above, wherein at least one of the segments is poly(ethylene glycol).
It is still another aspect of the present invention to provide a multicomponent network, as above, which is triphilic, i.e., hydrophilic, lipophilic, and oxyphilic.
It is yet another aspect of the present invention to provide a multicomponent network, as above, wherein the network is biocompatible and has excellent immunoisolatory properties, excellent mechanical properties, and excellent biostability.
It is a further aspect of the present invention to provide a tricomponent/tricontinuous network or membrane.
It is still a further aspect of the present invention to provide a tricomponent/tricontinuous network, as above, that is at least amphiphilic.
It is yet a further aspect of the present invention to provide a tricomponent/tricontinuous network, as above, which is triphilic.
At least one or more of the foregoing, together with the advantages thereof over the known art relating to polymeric networks, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.
In general, one or more aspects of the present invention may be accomplished by a multi-component network comprising the reaction product of at least a plurality of multifunctional, allyl terminated polyethylene glycols linked to a plurality of multifunctional siloxane compounds having at least two (2) SiH moieties for each siloxane compound.
One or more other aspects of the present invention may be accomplished by a multicomponent network comprising the hydrosilation reaction product of a plurality of ditelechelic, allyl-terminated polyethylene glycols, a plurality of ditelechelic, allyl-terminated polyisobutylenes, and a plurality of ditelechelic vinyl-terminated polydimethylsiloxanes, each linked to a plurality of pentamethylcyclopentasiloxanes having five SiH moieties for each of the pentamethylcyclopentasiloxanes.